1. Field of the Invention
The present invention relates generally to intravascular devices. More particularly, it concerns self-expandable woven intravascular devices for use as stents, occluders or filters, the methods of making the same, and the apparatus and methods for delivery of the same into a living creature.
2. Description of Related Art
Intravascular devices that serve as stents or filters constructed using a plain weave, such as the stent disclosed in U.S. Pat. No. 4,655,771 to Wallsten (hereinafter, the WALLSTENT), have a propensity to show a high-degree of elongation axially with diameter reduction. This is especially significant, when the angle of the crossing wires is close to the largest possible. The closer that the angle between the wires is to 180xc2x0, the more the corresponding elongation of the stent is at a given percentage of decrease in diameter. Any discrepancy between the diameters of the stent and the vessel can result in a considerable elongation of the stent. Simultaneously, the woven type stent has the largest expansile force and hence the biggest resistance to outer compression when the angle between the crossing wires is close to 180xc2x0. In some applications, such as outer compression by a space occupying lesion, the increased radial force may be advantageous. The disadvantage of a propensity for elongation is that great care must be taken when delivering such a stent in a vessel or non-vascular tubular structure in order to properly position it.
A further disadvantage of intravascular devices formed using a plain weave, is that they are often incapable of maintaining their shape when bent. For example, when such a stent is being delivered through a tortuous passageway with many turns, upon being bent, the weave of the stent tightens (e.g., the angle of the crossing wires approaches 180xc2x0). As a result of this tightening, the diameter of the stent increases and the length of the stent decreases. Consequently, the diameter of the stent may exceed the diameter of the vessel or structure through which it is traveling, impeding the delivery of the stent or causing the stent to lodge in the vessel. This problem may be due in part to the use of weave materials such as stainless steel, which exhibit poor shape memory. This problem may also be due to the free, unclosed wires used to form the stent. The free sharp ends can create potential complications by penetrating, or perforating the wall of the tubular structure where such a stent is placed. Further, steps that have been taken to eliminate the free, sharp ends, such as connection with U-shaped members using welding, glue or the like (Wallsten, 1987) are time-consuming and expensive. The delivery systems for such devices have also suffered from problems relating to the repositionability of the devices as they are delivered into position in the living creature.
In stenting long arterial segments, the contiguously decreasing diameter of the arterial system from the center to the periphery may pose problems. Woven stents with a uniform diameter will exert a substantial expansile force to the vessel wall along the tapered portion. Additionally, the stent may remain more elongated in the tapered portion. In a study where WALLSTENTs with a uniform diameter were used to bridge central venous obstruction in hemodialysis patients, it was found that the stents which were selected according to the size of the larger diameter central vein exerted considerably higher force to the wall of the smaller caliber subclavian vein (Vesely, 1997). Simultaneously, the length of the stents in the smaller caliber vein was longer than expected.
In the prior art, most of the filter designs except for the Bird""s Nest filter (Cook Inc., Bloomington, Ind.) have a conical shape and are anchored with multiple legs in the wall of the cava. The conical design is used because the main stream of the blood carries the thrombi from the lower part of the body through the center of the inferior vena cava. Therefore, all these devices are designed to have good filtration capacity at the center of the cava. The situation is quite different after some thrombi have been successfully captured. The center of the cava will no longer be patent and as a result, the blood will be diverted from the center to the periphery of the cava. The aforementioned designs, however, are not capable of catching thrombi effectively at the periphery of the lumen so the patients will practically be unprotected against subsequent peripheral embolization (Xian, 1995; Jaeger, 1998). Further, most of filters tend to be tilted in the cava which can deter their thrombus-capturing efficacy. Additionally, except for the Simon nitinol filter (C. R. Bard, New Jersey, N.J.) the aforementioned designs require a fairly large invasive delivery system of 10-F or larger.
The uniform caliber of cylindrical stents in the prior art used in the ureter, as well as the peristalsis arrested at the proximal end of the stent, has resulted in severe hyperlasia of the urothelium and eventually occlusion of the ureter.
Turning to occluders, percutaneous occlusion techniques have become indispensable tools in minimally invasive management of a wide range of pathological conditions. Use of permanent mechanical occlusion devices has been shown to be equivalent to that of surgical ligation. The Gianturco-Wallace stainless steel coil (Cook Inc., Bloomington, Ind.) has been the most widely used permanent, expandable intravascular occlusion device for transcatheter delivery (Gianturco et al., 1975).
Percutaneous coil embolization has been shown to be advantageous over traditional surgical procedures in treatment of life threatening hemorrhage due to trauma or obstetric emergencies (Schwartz et al., 1993; Teitelbaum et al., 1993; Selby Jr., 1992; Levey et al., 1991; Ben-Menachem et al., 1991; Vedantham et al., 1997). Furthermore, coils have been used alone or in combination with microvascular embolic agents for the treatment of vascular fistulas and malformations, tumors, and varices (Wallace et al., 1979; Hendrickx et al., 1995; Furuse et al., 1997; White et al., 1996; Sagara et al., 1998; Punekar et al., 1996). During the last few years, the transcatheter closure of the patent ductus arteriosus (PDA) with coils has become a frequently used technique (Hijazi and Geggel, 1994; Hijazi and Geggl, 1997).
Although coil type occlusion devices have shown at least a degree of utility, they have a number of drawbacks that could be significant in some applications. Intravascular stability of the coils has been shown to be highly dependent on proper matching of coil diameter with the diameter of the target vessel (Nancarrow et al., 1987), and with the exception of small vessels, a single coil rarely results in a stable occlusive thrombus (Hijazi and Geggel, 1994). Moreover, a long vascular segment is often obliterated because of the frequent need for multiple coils and the coils often remain elongated within the vessel because their unconstrained diameter is larger than the vascular lumen. Furthermore, delayed recanalization rates of 37%-57% have been reported in humans within 1-3 months after initially successful coil embolization (Sagara et al., 1998; O""Halpin et al., 1984; Schild et al., 1994).
These and other drawbacks have inspired modifications in the design and technique of coil embolization. Recently, detachable microcoils and macrocoils with controlled delivery have been designed to achieve a more compact conglomerate of the coil and to prevent migration by allowing optimal positioning of the coil before release (Zubillaga et al., 1994; Guglielmi et al., 1995; Marks et al., 1994; Reidy and Qureshi, 1996; Uzun et al., 1996; Tometzki et al., 1996; Dutton et al., 1995). However, since optimal arrangement of the coil alone may not prevent migration in some cases, such as high flow conditions or venous placement, a coil anchoring system has been devised (Kxc3x3nya et al., 1998). Although an anchoring system may stabilize a coil conglomerate within the vasculature, significantly reducing or eliminating the possibility of coil migration, such a system may render the coil non-repositionable.
Several different non-coil devices have been designed to achieve a more stable, limited size plug with higher hemostatic efficiency particularly for transcatheter closure of larger vessels (Schmitz-Rode et al., 1993; Kato et al., 1997; Kxc3x3nya et al., 1999) and PDAs (Pozza et al., 1995; Magal et al., 1989; Grifka et al., 1996). Recently, initial clinical experiences with a new self-expanding nitinol-mesh PDA occluder have been reported (Sharafuddin et al., 1996; Masura et al., 1998). A similar self-expanding, repositionable quadruple-disc device constructed of a braided nitinol mesh and polyester fibers has been reported to be superior to standard Gianturco coils in experimental occlusion of mid-size arteries (Sharaffuddin et al., 1996).
Although such non-coil devices may be repositionable, they too exhibit drawbacks. For instance, the quadruple-disc device is several centimeters long in an elongated fashion, making difficult to keep the superselective position of the catheter tip during deployment. The multiple rigid connections between the layers and the relative long and rigid connection between the occluder and the delivery cable further increase this drawback. Although the nitinol mesh-PDA occluder has demonstrated utility, its proper placement requires a proper match both in size and shape between the occluder and the lesion to be occluded. The type and quality of the connection between the occluder and the delivery cable is the same as in the quadruple-disc design. A common disadvantage of both designs is that they lack guidewire compatibility. As a result, a delivery catheter must often be navigated to the site of occlusion first before an occluder may be loaded into the catheter and delivered through it. Another relative disadvantage of both devices is their cost of manufacturing.
Percutaneous catheter technique for permanent closure of isolated persistently patent ductus arteriosus (PDA) is now a treatment of choice among doctors, obviating open surgery. The configuration of the PDA varies considerably. A majority of PDAs tend to have a funnel or conical shape due to ductal smooth muscle constriction at the pulmonary artery insertion, although narrowings in the middle or aortic ends can be observed (Krichenko, 1989). That is the reason why not only the size, but also the configuration, of the lesion plays a significant role in selecting an appropriate occluding device. Except from the small caliber lesions (with a maximum diameter of 2.5 mm or 3.3 mm, respectively), where some authors have achieved successful closure of the PDA with Gianturco coils (Cambier, 1992; Lloyd, 1993; Sommer, 1994), Rashkind""s xe2x80x9cdouble umbrellaxe2x80x9d occluder is the most often used device for this purpose (Rashkind, 1987; Hosking, 1991; Latson, 1991; Wessel, 1988; Report of the European Registry, 1992). It is available in two sizes (with a diameter of 12 mm and 17 mm) which require a 8-F and 11-F delivery system, respectively.
In the majority of cases, the deployment of the traditional PDA device is performed from a femoral vein access (Report of the European Registry, 1992). Because of the size of the delivery sheath, such a device is not suitable for the treatment of patients with a body weight of less than 8 kg. Using even a larger umbrella, this procedure is not recommended for the treatment of the lesions with a diameter of 8 mm or above (Latson, 1991). About 80% of unselected patients with isolated PDA are candidates for the Rashkind device using the aforementioned criteria (Latson, 1991). With the Rashkind device, the proportion of patients with residual flow through the lesion fell from 76% immediately after implantation to 47% by the day after implantation and to 17% by a year after implantation (Report of the European Registry, 1992). According to some authors the residual flow carries a potential risk of infective endocarditis and should be avoided if possible. Its abolishment can be achieved by implantation of another device or surgery.
One of the main drawbacks of the Rashkind umbrella is that it is not suitable for occlusion of all types of PDA. Preferably, it is used to occlude short PDAs with relatively wide end-openings. Its two discs cover both the pulmonary and the aortic opening of the PDA. Longer PDA may hinder the discs to be positioned in the proper way, that is, parallel to each other, thereby deteriorating its self-anchoring. Another disadvantage of the umbrella is that the occluding capacity of the design depends exclusively on the thrombogenicity of the porous Dacron material, frequently resulting in partial and lengthy occlusion.
For the majority of patients with urinary leakage and/or fistulas (mainly due to tumor propagation to their ureters), the diversion of urine is currently performed by a percutaneous transrenal approach together with ureteral occlusion. Formerly, detachable and non detachable balloons were used for this purpose, but they did not cause satisfactory ureteral occlusion. Migration as well as deflation of the balloons occurred relatively frequently (Gunter, 1984; Papanicolau, 1985) leading to recurrence of the urine leakage. A silicone ureteral occluder was developed and used with only limited success because of device migration (Sanchez, 1988). This resulted in repositioning and consequent incomplete ureteral occlusion. It appears that the best results have been accomplished with Gianturco coils and Gelfoam embolization (Gaylord, 1989; Bing, 1992 a; Farrel, 1996). Even with multiple coil placements, together with Gelfoam plugs, the ureteral occlusion may sometimes be achieved for only weeks or months, and was attributed mostly to the induced urothelial hyperplasia (Bing, 1992 b). Coil migration was frequently encountered in these studies. The lack of appropriate self-anchoring results in coil migration which eventually deteriorates the occlusive effect.
Problems pointed out in the foregoing are not intended to be exhaustive but rather are among many that tend to impair the effectiveness of previously known stents, occluders and filters. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that previous techniques appearing in the art have not been altogether satisfactory, particularly in providing flexible, self-expanding, repositionable stents, occluders and filters.
The present invention overcomes the problems inherent in the prior art by providing a self-expandable, repositionable device for use as a stent, an occluder, or a filter which may be formed using a plain weave, and may have closed structures at both its ends.
In one respect, the invention is a device that includes, but is not limited to, a plurality of shape memory wires woven together to form a body suitable for implantation into an anatomical structure. The body has first and second ends. The shape memory wires cross each other to form a plurality of angles, at least one of the angles being obtuse. Both ends of at least one shape memory wire are located proximate one end of the body. The value of the obtuse angle is increased when the body is axially compressed.
The shape memory wires may be made of nitinol. The shape memory wires may be made of FePt, FePd or FeNiCoTi. The shape memory wires may be made of FeNiC, FeMnSi or FeMnSiCrNi. The shape memory wires may each have a diameter ranging in size from about 0.006 inches to about 0.012 inches. The plurality of shape memory wires may include at least 6 shape memory wires. The body may have a tubular shape with a substantially uniform diameter. The body may have a tapered shape with a diameter that decreases from one end of the body to the other end of the body. The body may have a generally hourglass shape. As used herein, xe2x80x9ca generally hourglassxe2x80x9d shape is a shape that resembles a body having two ends that are larger in terms of cross-sectional area than a mid-portion located therebetween. Such shapes include those resembling traditional hourglasses or dumbbells, for example. The body may be woven by hand. The body may be woven by a machine, such as a braiding machine.
The device may also include, but is not limited to, a graft material attached to the body. The graft material may be made from woven polyester. The graft material may be made from Dacron. The graft material may be made from polyurethane. The graft material may be made from PTFE. The graft material may partially cover the body. As used herein, a graft material that xe2x80x9cpartially coversxe2x80x9d a body is attached to the body such that a portion of the wire or wires forming the body are left bare or exposed. As a result of only partially covering a body, blood or other bodily fluids may flow through the bare portion of the body relatively unimpeded by the graft material.
The device may also include, but is not limited to, a first tube that is configured to accept a guide wire and a second tube that is configured to fit over the first tube. Prior to delivering the body into an anatomical structure, the second tube is placed over the first tube, one end of the body is secured to the first tube and the other end of the body is secured to the second tube.
In another respect, the invention is a device that includes, but is not limited to, a body suitable for implantation into an anatomical structure. The body has a first end, a second end and is defined by at least n shape memory wires, wherein n is greater than one. The n shape memory wires are arranged such that the body includes a first portion. The first portion includes a first woven portion and at least one strut. The shape memory wires of the first woven portion cross each other to form a plurality of angles, at least one of the angles being obtuse. Both ends of at least one shape memory wire are located proximate one end of the body. The value of the obtuse angle is increased when the body is axially compressed.
The shape memory wires may be made from nitinol. The shape memory wires may be made from FePt, FePd or FeNiCoTi. The shape memory wires may be made of FeNiC, FeMnSi or FeMnSiCrNi. The first portion may include a first woven portion separated from a second woven portion by multiple first struts.
The body may also include, but is not limited to, a second portion located adjacent to the first portion. The second portion includes a second woven portion. The second portion has n+x shape memory wires, and x is at least one. The first portion may have a generally domed shape. The first woven portion may have a generally domed shape and the multiple first struts may be bent slightly so as to increase the self-anchoring capability of the body in an anatomical structure. The first portion may also include a third woven portion separated from the second woven portion by multiple second struts. The first and third woven portions may have generally domed shapes.
The device may also include, but is not limited to, a graft material attached to the body. The graft material comprises may be made from woven polyester. The graft material may be made from Dacron. The graft material may be made from polyurethane. The graft material may be made from PTFE. The graft material may partially cover the body.
The device may also include, but is not limited to, a first tube that is configured to accept a guide wire and a second tube that is configured to fit over the first tube. Prior to delivering the body into an anatomical structure, the second tube is placed over the first tube, one end of the body is secured to the first tube and the other end of the body is secured to the second tube.
In another respect, the invention is a device that includes, but is not limited to, a plurality of biodegradable filaments woven together to form a self-expanding body suitable for implantation into an anatomical structure. The self-expanding body has a first end and a second end. The biodegradable filaments cross each other to form a plurality of angles, at least one which is obtuse. The value of the obtuse angle is increased when the body is axially compressed.
The biodegradable filaments may be made from polyglycolic acid. The biodegradable filaments may be made from poly-L-lactic acid. The biodegradable filaments may be made from a polyorthoester. The biodegradable filaments may be made from a polyanhydride. The biodegradable filaments may be made from a polyiminocarbonate. The biodegradable filaments may be made from an inorganic calcium phosphate. The biodegradable filaments may include about 0.05 to 0.25 percent by weight of calcium oxide, calcium hydroxide, calcium carbonate, calcium phosphate, magnesium oxide, magnesium hydroxide, magnesium carbonate, magnesium phosphate, sodium phosphate or potassium sulfate. The biodegradable filaments may be made from a polymer having about 15 to about 30 mole percent glycolide. At least one of the biodegradable filaments may be made from paclitaxel, docetaxel or heparin. Both ends of at least one biodegradable filament may be located proximate the first end of the self-expanding body. Each end of the self-expanding body may include at least one closed structure.
The device may also include, but is not limited to, at least one shape memory wire secured to the self-expanding body. Both ends of the one shape memory wire may be located proximate one end of the self-expanding body.
In another respect, the invention is a method of creating a body suitable for implantation into an anatomical structure. The body has two end ends. The method includes, but is not limited to, bending the shape memory wires in a plurality of shape memory wires to create bent portions in the shape memory wires. The bent portions are arranged to define one end of the body. Each shape memory wire has two ends. The method also includes, but is not limited to, weaving the ends of the shape memory wires to create the body such that the shape memory wires cross each other to form a plurality of angles, at least one of the angles being obtuse. The value of the obtuse angle is increased when the body is axially compressed.
The bent portions may be bends or loops. The shape memory wires may be made from nitinol. The shape memory wires may be made of FePt, FePd or FeNiCoTi. The shape memory wires may be made of FeNiC, FeMnSi or FeMnSiCrNi. The shape memory wires may each have a diameter ranging in size from about 0.006 inches to about 0.012 inches. The plurality of shape memory wires may include at least 6 shape memory wires. The body may have a tubular shape with a substantially uniform diameter. The body may have a tapered shape with a diameter that decreases from one end of the body to the other end of the body. The body may have a generally hourglass shape. The body may be woven by hand. The body may be woven by a machine, such as a braiding machine.
In another respect, the invention is a method of creating a body suitable for implantation into an anatomical structure. The body has two ends. The method includes, but is not limited to, providing a weaving system that includes a template having first template projections. The method also includes, but is not limited to, bending shape memory wires around the first template projections to create bent portions in the shape memory wires. The bent portions are arranged to define one end of the body. Each shape memory wire has two ends. The method also includes, but is not limited to, weaving the ends of the shape memory wires around the template to create the body such that the shape memory wires cross each other to form a plurality of angles, at least one of the angles being obtuse. The value of the obtuse angle is increased when the body is axially compressed.
The first template projections may be tabs. The first template projections may be pins. The pins may be attached to a ring engaged with the template. The weaving system may also include, but is not limited to, a first weaving plate configured to rotate in a first direction during the weaving. The weaving system may also include, but is not limited to, first bobbins arranged on the first weaving plate, and one end of each shape memory wire is attached to each first bobbin prior to the weaving. The weaving system may also include, but is not limited to, a second weaving plate configured to rotate in a second direction during the weaving, and the second weaving plate is spaced apart from the first weaving plate. The weaving system may also include, but is not limited to, second bobbins arranged on the second weaving plate, and one end of each shape memory wire is attached to each second bobbin prior to the weaving. The method may also include, but is not limited to, securing the shape memory wires to the template. The method may also include, but is not limited to, forming closed structures with the ends of the shape memory wires. The closed structures may be arranged to define the other end of the body. The method may also include, but is not limited to, heating the body and the template.
In another respect, the invention is a device for delivering an axially and radially expandable woven body having two ends into an anatomical structure. The device includes, but is not limited to, a first tube configured to accept a guide wire, and a second tube configured to fit over the first tube. When the tubes are used for delivering the axially and radially expandable woven body, one end of the axially and radially expandable woven body is secured to the outside of the first tube and the other end of the axially and radially expandable woven body is secured to the outside of the second tube.
The first tube may be made from NYLON or TEFLON. The second tube may be made from NYLON or TEFLON. The device may also include, but is not limited to, a guide wire configured to be placed within the first tube. The outer diameter of the first tube may range in size from 3 French to 7 French. The outer diameter of the second tube may range in size from 5 French to 9 French. The device may also include, but is not limited to, a push-button release/lock mechanism configured to secure the first tube to the second tube. The device may also include, but is not limited to, an end fitting having a side arm. The end fitting is configured to be secured to the first tube. The first tube may be provided with at least one pair of first tube holes through which a first securing wire may be threaded. The pair of first tube holes may be positioned proximate one end of the first tube. The second tube may be provided with at least one pair of second tube holes through which a second securing wire may be threaded. The pair of second tube holes may be positioned proximate one end of the second tube.
In another respect, the invention is a device for delivering an axially and radially expandable woven body having two ends into an anatomical structure. The device includes, but is not limited to, a first tube configured to accept a guide wire. The first tube has at least one pair of first tube holes that are positioned proximate one end of the first tube. The device also includes, but is not limited to, a second tube configured to fit over the first tube. The second tube has at least one pair of second tube holes that are positioned proximate one end of the second tube. The device also includes, but is not limited to, a first securing wire configured to be threaded through the pair of first tube holes. The device also includes, but is not limited to, a second securing wire configured to be threaded through the pair of second tube holes. When the tubes are used for delivering the axially and radially expandable woven body, one end of the axially and radially expandable woven body is secured to the outside of the first tube with the first securing wire and the other end of the axially and radially expandable woven body is secured to the outside of the second tube with the second securing wire.
In another respect, the invention is an occluding system that includes, but is not limited to, a plurality of shape memory wires woven together to form a body useful for occluding an anatomical structure. The body has first and second ends. Both ends of at least one shape memory wire are located proximate one end of the body. The shape memory wires cross each other to form a plurality of angles, at least one of the angles being obtuse. The value of the obtuse angle is increased when the body is axially compressed.
The shape memory wires may be made from nitinol. The occluding system may also include, but is not limited to, an occluding agent enclosed within the body. The occluding agent may include one or more threads of polyester. The occluding agent may also include, but is not limited to, one or more threads of DACRON. The occluding system may also include a jacket coupled to the body. The jacket may be made from silicone. The jacket may be made from polyurethane. The occluding system may also include, but is not limited to, a first tube configured to accept a guide wire, and a second tube configured to fit over the first tube. Prior to delivering the body into an anatomical structure, one end of the body is secured to the outside of the first tube and the other end of the body is secured to the outside of the second tube.
In another respect, the invention is a device that includes, but is not limited to, a body suitable for implantation into an anatomical structure. The body has an axis, a first end and a second end. The body is made from a shape memory wire that has a first segment and a second segment. The segments are separated by a bend in the shape memory wire that is located proximate one end of the body. The first segment extends helically in a first direction around the axis toward the other end of the body. The second segment extends helically in a second direction around the axis toward the other end of the body. The first and second segments cross each other in a plurality of locations.
The first segment may be positioned farther from the axis than the second segment at at least one location. The first segment may be positioned farther from the axis than the second segment at each location. The shape memory wire may be made from nitinol. The device may also include a first tube configured to accept a guide wire, and a second tube configured to fit over the first tube. Prior to delivering the body into an anatomical structure, one end of the body is secured to the outside of the first tube and the other end of the body is secured to the outside of the second tube.
In another respect, the invention is a device that includes, but is not limited to, a body suitable for implantation into an anatomical structure. The body has a first end and a second end. The body is formed from a shape memory wire that has a first segment and a second segment. The segments are separated by a bend in the wire that is located proximate one end of the body. The first segment and second segments are arranged to form loops and twisted segments such that at least two contiguous loops are separated from another loop by a twisted segment. The definition of xe2x80x9ccontiguousxe2x80x9d is set forth below with reference to the figures herein for the sake of clarity.
At least three contiguous loops may be separated from another loop by a twisted segment. At least four contiguous loops may be separated from another loop by a twisted segment. At least two contiguous loops may be separated from two other contiguous loops by a twisted segment. The shape memory wire may be made from nitinol. The device may also include, but is not limited to, a first tube configured to accept a guide wire, and a second tube configured to fit over the first tube. Prior to delivering the body into an anatomical structure, one end of the body is secured to the outside of the first tube and the other end of the body is secured to the outside of the second tube.
In another respect, the invention is a device that includes a body suitable for implantation into an anatomical structure. The body has, but is not limited to, two ends and is formed from a shape memory wire that has a first segment and a second segment. The segments are separated by a bend in the wire that is located proximate one end of the body. The segments are positioned adjacent to each other in loop-defining locations. The segments also extend between the loop-defining locations in spaced relation to each other so as form at least two loops. At least one of the at least two loops has a compressed shape. The definition of a xe2x80x9ccompressedxe2x80x9d shape is set forth below with reference to the figures herein for the sake of clarity.
The shape memory wire may be made from nitinol. The segments may be secured together using welds at the loop-defining locations. The segments may be secured together with collars at the loop-defining locations. The body may also include, but is not limited to, at least one coil placed over at least a portion of one of the segments, and, as a result, the body may be used as an occluder. The body may also include at least one fiber attached to the coil. The device may also include, but is not limited to, a first tube configured to accept a guide wire, and a second tube configured to fit over the first tube. Prior to delivering the body into an anatomical structure, one end of the body is secured to the outside of the first tube and the other end of the body is secured to the outside of the second tube.
The present invention also provides a delivery system that may secure both the proximal and distal ends of the stent, occluder or filter. Advantageously, this delivery system allows the stent, occluder or filter to be easily repositioned as it is being delivered into place. As a result, the stent, occluder or filter may be more precisely positioned within the living creature.
One advantage of the present invention is the unique fixation method of the tapered stent. The tapered shape of the stent allows the stent to be fixed in a tapered vessel or tubular structure with less radial or expansile force than a straight stent might exhibit, thus potentially resulting in a less hyperplastic intimal reaction.
The straight stent of the present invention exhibits a high expansile force and thus a large capability of withstanding outer compression. This may be especially advantageous in tumorous stenoses, or fibrous strictures (including radiation-induced stenoses) where stents with inadequate expansile forces can be easily compressed and/or are incapable of assuming their nominal shape and diameter. In some cases, even the stenoses of arteriosclerotic origin can be so calcified (e.g., iliac or renal artery stenoses) that extra radial force is required from the stent to hold the patency of the vessel. Furthermore, the woven intravascular devices of the present invention are also able to return to their original, unconstrained shape after being bent, even maximally.
Advantageously, the stents, occluders and filters of the present invention do not possess free, sharp wire ends. Thus, many potential complications are eliminated (Prahlow, 1997). Additionally, the tight mesh of the stents of the present invention coupled with the use of nitinol wires, for example, makes them easy to monitor under fluoroscopy.
The present invention also includes a group of self-expanding, self-centering cava filters woven from materials as described above such that a coherent element is formed that without the use of a joint or attachment between the portions of the filters. The cava filters of the present invention provide increased filtrating efficiency not only at the center but also at the periphery of the cava. Additionally, the hourglass filter of the present invention utilizes multiple filtration levels. The cava filters of the present invention are able to self-center due to the symmetrical nature of their design and their potentially flared base.
The cava filters of the present invention may utilize a relatively small, 7 French delivery catheter or sheath. Additionally, the superb flexibility of the cava filters makes it possible to deliver them via any of the possible access sites of the human body (femoral, jugular, antecubital veins).
The present invention also includes a bi-iliac filter (xe2x80x9cBI filterxe2x80x9d) that is a low-profile, self-expanding, flexible, temporary filter which may be woven from a number of superelastic or shape memory alloys. The BI filter is a type of temporary filter that can be deployed from either femoral vein, and it can filtrate the blood at the iliac veins/inferior cava junction. The BI filter of the present invention typically works at a low level of venous circulation. Advantageously, the BI filter simultaneously filters all the blood coming from both iliac veins, achieving almost 100% filtration. Further, the use of the BI filter is particularly beneficial in perioperative and posttraumatic cases.
The inverse U-shape of the BI filter together with the expansile force of the tubular weave ensures firm position along the iliac/cava junction. A further advantage of the present invention is that the BI filter may utilize a relatively small, 7 French delivery catheter or sheath. Further, due to the flexibility of the mesh of the BI filter, the delivery system thereof may be advanced from ipsi- to contralateral iliac vein. As with the cava filters, the BI filter may possess a non-ferromagnetic character making it MRI compatible.
The BI filter is suitable for temporary filtration. The BI filter allows for removal of the entrapped thrombi safely and successfully before removal of the filter. Using an adequately sized sheath, the small thrombus fragments entrapped within the mesh could also be removed together with the filter.
The stents of the present invention can be advantageously covered with materials such as silicone, polyurethane, and/or an anticancer coating agent that allow the stents to reduce the possibility of restenosis after delivery, and which also allow the stents to be used in stenting malignant stenoses, for example. The filters of the present invention may also be covered with anticoagulant coating agents.
Ureter strictures/compression/occlusion may be stented with these uncovered and/or covered stents; in particular, the use of a long tapered stent may advantageously match the special conditions posed by the different caliber and distensibility of the different segments of the ureter as well as the constant peristalsis.
The stents of the present invention can also be used in some non-vascular applications including biliary tree and tracheo-bronchial system if the lesion does not require a bifurcated stent.
The stents, occluders and filters of the present invention may be used in many different applications. They provide the advantages of superb flexibility, repositionability/removability, and precise positionability.